[Dhanik desai]

Good morning I am a beginner in CFD, I am using Ansys fluent, I have 2 inlets and 1 outlet condition (It is tee joint) I want to know as per boundary conditions name Inlet is considered as velocity inlet , but for outlet why it is considered as "pressure outlet"?

thank you

[vinerm]

The objective of CFD is to predict the fields, i.e., variation of pressure, velocity, etc. over the space and also over the time, if required. Velocity at the outlet is not known a priori; average velocity could be known but if the goal is to predict only average velocity, then CFD is not required. Usually, the variation in the velocity is required to be predicted at the outlet. Hence, velocity is unknown, however, the pressure may or may not be known. If a duct is open to the atmosphere, then the average gauge pressure is 0. So, pressure outlet is used most of the times. Sometimes, velocity or mass flow rate may be known. So, it is not that always pressure outlet is used at the outlet. It could be any of the boundary conditions; it all depends on the objective of the simulation and the available information.